Cutting old propane/butane tanks

I'll let someone else tackle the "cutting the tank" part of the question.

When using it for decorative bits and the like, sure. It gets dicey when you start loading it up structurally near the limits of the materal (like, say, for actually re-enforcing concrete), but I suspect for holding up a mostly-empty butane tank, you'll be nowhere near that and it will hold up fine.

--Glenn Lyford

Balders wrote: ...

Prep is unnecessary UNLESS you're going to cut with oxy-fuel. In that case, the tank must be purged, as introducing oxygen from the torch can create an explosive mixture. Otherwise the pure propane/butane in the tank can't burn without oxygen. Some may seep out & ignite, but inconsequentially.

I use a cut off disc in an angle grinder to make a slit-hole & then a recip saw with a metal cutting blade. Works well.

Bob

Rebar can be a problem: the common stuff is either c40 at 40 kpsi and .4% carbon or C60 grade at 60 kpsi and .6% carbon. Either one will get brittle if it is cooled rapidly. If you do a big weld, let the whole bar get it nice and red, let it cool slowly, it may not be a problem. If you do a small stitch weld, the HAZ is likely to be very brittle. These effects are not consistent. Sometimes it works fine, other times it snaps when you tap it with a hammer.

There are some weldable grades of rebar, price is much higher, it w> Hi guys & girls,

Remember Rebar is junk metal to a certain alloy. It might be junk white to ball bearing in inches. It might be great. One can't tell unless one specifies to the steel company on the grade - e.g. for bridge and high reliability construction.

Mart> Hi guys & girls,

I don't want anyone suing me, but the tank only has to be purged and let sit for awhile as propane evaporates at room temperature.

Therefore, if you just let it sit for awhile open, it will be empty and all the gas will be gone. Gas is the key things here. All the gas evaporates fairly fast, just like when you light your BBq. No gas, no flame. Easiest way to explain it. I learned this from arm chairing a BBQ list, called the poach, which is mostly defunct now, but if you find their FAQ at their web page you can likely fine more. If you can find Big Jim he specializes in lazy Q which is a propane tank with a gas burner.

The hardest part is trusting to cut into the tank with a flame. Yipes. :O)

Why? Its dead soft, and they hold it together with tie wire in most applications.

for actually re-enforcing concrete), but I suspect

Rebar is NOT dead soft!!! It is high carbon, not uniform from one stick to the next, some is very hard. You take your chances when welding it.

I do a demo with it: Do a big weld with lots of weave on a sample, get it good and hot. Toss it immediately into a bucket of water. It will shatter on the floor when you drop it or hit it with a hammer. It is a far out case but everyone remembers it.

That depends on the grade of rebar. Some rebar is made from new stock but most common rebar is recycled material and could quite well act as you have experienced. Steve

Our big mill around here is North Star Steel. They do mostly hot rolled products, huge runs of rebar. Everything is recycled, mostly car bodies from what I've seen.

I talked to one of their QA folks. They make the C40 grade which is supposed to be 40kpsi but they just adjust it to .4% carbon and roll it out. Ditto for the C60 grade at .6% carbon. .6% carbon is enough to start making it very dependent on heat treating cycles, especially HAZ.

None of this applies to the weldable grades of rebar which are much more money.

I've run across the same issues in hot rolled flat bar stock. Took out 3 blades on the horizontal band saw before I isolated the offending

Up North wrote:

Not quite! The liquid propane will indeed evaporate, but the tank will still be full of propane vapors/gas, at atmospheric pressure. This is what needs to be purged before cutting with a torch. And the vapor/gas will burn (very slowly) as it oozes out of the cut, if ignited.

Your use of the word "gas" is confusing. You say "All the gas evaporates fairly fast ...". Liquid evaporates. Gas is what you have after liquid evaporates.

Bob

Thanks for all the replies :)

I'll keep you posted although it may be a while until I do it.

I've also had the idea of using old chain for the legs/tail/arms and welding the links using my buzz box.

Should be fun & my neighbours are going to wonder WTH is he up to. Might see if I can have the use of a plasma cutter to cut out the facial details. Although, would a standard jigsaw with a metal blade be ok here?